


Abiogenesis

by alethiometry



Category: Supernatural
Genre: Background Relationships, Heaven, M/M, Polyamory, Post-Canon
Language: English
Status: Completed
Published: 2016-12-20
Updated: 2016-12-20
Packaged: 2018-09-09 23:59:13
Rating: General Audiences
Warnings: Major Character Death
Chapters: 1
Words: 2,692
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/8918641
Author URL: https://archiveofourown.org/users/alethiometry/pseuds/alethiometry
Summary: The Winchesters' souls have long since ascended to Heaven, but that doesn't mean they're completely gone from Earth. Castiel watches them — or traces of them — on both planes, and waits for Sam to let him in.





	

**Author's Note:**

  * For [De_Nugis](https://archiveofourown.org/users/De_Nugis/gifts).



> A _huge_ shoutout to [story_monger](http://story_monger.livejournal.com) for all her patience and help in beta-ing and fact-checking every detail of this fic! Thank you so much!

 

If Castiel were to describe the Winchesters’ shared Heaven in one word, it would be _noisy_. It’s a lesson he’s learned time and again: even a phenomenon as seemingly final as death (permanent, this time) must yield in the face of sibling bickering.

This time, it seems to be regarding the cultural superiority of pirates versus ninjas. Which seems to Castiel a particularly pointless argument given the fact that, for a time, there did exist a smattering of seafaring mercenaries across East and Southeast Asia trained specially in the stealth arts. Part of him wonders if he should point this out and quell the noise. Another part of him enjoys the spectacle. Sam and Dean are very animated debaters.

Not that it ever gets out of hand; both brothers are accustomed enough to Heaven’s mechanics by this point that if the bickering ever becomes too contentious, they can each find the Axis Mundi with relative ease and retreat into their own private spaces. Dean is currently cruising down Route 66, windows rolled down and Led Zeppelin on blast. Sometimes the road will lead him to the Grand Canyon, other times to Harvelle’s Roadhouse, or even to a little two-story, two-bedroom house in Cicero, Indiana. He’ll go wherever he needs or wants to go, though he may not even be consciously aware of it until he’s arrived. And when he’s ready to return, the road will curve gently back to Lebanon, straight into the garage of the Men of Letters bunker where he and Sam continue to share their afterlife.

Heaven is nothing if not convenient.

Castiel goes to find Sam in his bedroom, as it were, and tries the door. It’s sealed to him, as it sometimes is, and that’s how he knows that the bedroom on the other side of the door isn’t a part of the bunker at all, but one in Palo Alto, California that burned to the ground long ago.

He wonders how many of his brothers and sisters have felt the envy that he sometimes feels, whenever Sam slips away to be with Jessica, or Amelia, or Madison. It’s a human emotion — a deadly sin, even, though any entity with the authority and power to enforce that distinction has long since left any known dimension — which perhaps speaks, more than anything else, to the fact that Castiel has spent a disproportionate amount of his life in the company of humans. And so it’s Castiel’s misfortune that he’s so intimately aware of the mechanics of Heaven that he knows exactly where Sam is now, and with whom.

Because Heaven isn’t as cleanly regulated as the Winchesters had once believed; soulmates exist, but not with the same sense of exclusivity that Ash, in his limited understanding and experience, had explained. It’s a fluid thing, adapting to the needs of each soul. Nor is it always in a romantic sense. Sam and Dean share a large part of Heaven with one another, it’s true, and with Castiel. But there are also parts of their own individual Heavens that overlap with those of their loved ones. There’s a part of Heaven that they share with their parents, for example, and another one for Dean and Ben and Lisa, and one for Sam and Jessica.

 _It’s not polygamy, strictly speaking,_ Castiel explained when they first arrived, newly dead and wholly perplexed, _nor is it infidelity. It just — is what it is. You’ll get used to it._

And, after a while, they did. And it would not be inaccurate to say that Castiel was more than a little pleased to find a small corner of Sam’s Heaven dedicated solely to the two of them, together.

But Sam is his own person, and Castiel won’t begrudge him his need to revisit any of his other happy memories, even if — _especially_ if — those memories don’t include him. Not when there was a time, long ago but fresh in memory, when his own kin wouldn’t have allowed Sam into Heaven at all. So as far as Castiel is concerned, Sam can do whatever he wants. That is, after all, one of the perks of ascending into eternal paradise. And Sam will come to him when he’s ready. He always does. They have nothing but time.

Still, it was worth a try. About half the time that Sam retreats behind that door, Castiel is able to join him in the bunker bedroom with which he’s become so familiar. It’s inane, he knows, to lie in bed and watch nature documentaries with Sam when he knows more about the intrinsic mechanics of the cosmos than even the most acclaimed names at BBC or PBS. But there’s a certain comfort in the self-reflective nature of the medium. It’s humanity at its best: investigative and inquisitive, critical and creative. Intimately engaged with the world at large.

It’s a world that, time and again, he’s watched the Winchesters save. He thinks it does some good to show Sam this.

He wishes he could show Sam the world as it is now.

It’s been eons since the Winchesters died for the last time — indeed, since humanity as they knew it walked the earth. Human history in all its microcosmic intricacies is short enough, relatively speaking, that it can be perceived in a linear fashion; the universe at large, however, operates on a cyclical scale, an endless rotation of creation-evolution-apotheosis-decline. And right now, on the planet that was once called Earth, life has just begun to emerge once more.

Castiel decides he wants to watch for a while.

 

———

 

 _Don’t step on that fish, Castiel,_ he can still hear his brother warning him, though it will be several million years before anything resembling fish will swim in this new primordial sea. There’s a stillness here, a grandiosity that dwarfs even Castiel’s true form. Impressive as they are to humans, awesome as their power may be to behold, angels still barely register on the geologic-cosmic scale. He’d once used the Chrysler Building in reference to himself, to his relative size — but what is a mere skyscraper next to soaring Himalayan peaks, or the deepest, darkest crevasses of the Mariana’s Trench?

Far more impressive than angelic forms, he thinks, are the physical marks that certain human souls can leave behind.

It’s an exceedingly rare occurrence; always has been. It just wouldn’t make cosmic sense for each and every human to leave some imprint of his or her soul upon ascension into Heaven. The imprints, after all, have a tendency to take on the qualities of their respective souls: a reactivated volcano, a magnetic anomaly. It’s unsustainable. There’s a fine line between chaos theory and utter pandemonium.

The Winchesters, however, have always been the exception. Where others have come and gone with little more than varied ripple effects of influence that waned as humanity itself waned, Sam and Dean have etched their marks so deeply into the fabric of creation that Castiel can still feel the aftershocks of their souls here, at the bottom of the primordial ocean that was once a continent called North America.

He finds Dean, or the echoes of Dean, in the sediment that he kicks up in swirling puffs as he walks across what used to be Arizona. He wonders if the more concentrated areas of Dean have any correlation whatsoever with major highways that once crisscrossed the land; he comes to the unsupported and unsubstantiated conclusion that yes, they must. He likes the idea of it, and so he will choose to believe it. If he’s learned anything from the Winchesters, it’s that faith itself carries a certain power; it doesn’t matter so much what that faith is placed in, as long as it’s there in some form. It gives you strength and conviction. Helps you to know yourself and where you stand, even when your surroundings have become utterly alien, as they are now. And so Castiel has faith now that what’s left of Dean here is a reflection of what Dean was to him in life and continues to be in Heaven: a friend, a guardian, a protector.

In another billion or so years, this sediment will solidify and rise above the waters to see the light of day: mountains and valleys, ores and minerals. Soil, even. Some intractable essence of Dean’s being preserved here forever. Waiting, always, to guard and nurture and connect in his own roundabout and stubborn way.

Castiel follows the veins of Dean’s essence to where it’s concentrated at the rim of what used to be the Grand Canyon. The water is much warmer here, as is the sediment when he kneels down and sifts it between his fingers, and as he pushes off from the rim and allows himself to sink further into the canyon, he can feel the temperature rising. And he sees, with the set of eyes focused specifically to see through the murky darkness, the spots at the base of the canyon where the earth’s crust has worn thin from a rising plume of magma beneath it — so thin that even those eyes have to squint to make out the hairline cracks beginning to split; floes of stone and sand and soil upon a molten, simmering sea.

These hydrothermal vents are the only source of heat this deep into the ocean; it was from here that life first emerged all those eons ago, and it is from here that it will come again.

It is here that he finds Sam.

Sam is the heat from the vents: gentle and scorching in equal turns, at once magnificent and terrifying. Unaware of his own power as it flares and ebbs. Volatile. He sustains what will become the first living beings on this new Earth, yet he also tests them, pushes their boundaries. Sometimes too far, though that too is to be expected. An undeniable goodness, but also a darkness, a potential for great destruction. Every duality here, every conflicting extreme that should be paradoxical yet somehow fits together perfectly — it’s so patently _Sam_ that it’s all Castiel can do to keep himself from diving ever deeper into the canyon, to the source of the life-giving heat that is the after-effect of Sam, and let himself disintegrate into it, grace and all.

He finds an outcropping on the canyon wall and settles in. Thousands of cubic meters of water bear down on his angelic form, far less dense than the human body, yet he feels little of it. He sits still in the water and waits for life to take shape.

A thousand meters more below him, mitochondria begin to metabolize. One cell, emboldened by the rising temperature, engulfs its neighbor. Castiel closes half of his eyes, the rest fixated on the activity below, and sinks into a half-sleep as the ebbs and flows of rising heat currents caress his outstretched wings.

He thinks of gentle, calloused fingers brushing lightly on his arm and soft, sighing breaths against his neck.

 

———

 

Castiel wakes to the scuttling of paramecia across his hands. The heat has flared up again, and the first true life forms are scrambling for shelter, lest they be incinerated. It’s little more than mechanical instinct for now, but still there’s a will. To live, to multiply. An intrinsic drive, in these clamoring cells, to play a role in the course of evolution, no matter how minuscule.

He places the cells up and away from the heat source, on a small ledge coated in gentle sediment. Some of them burrow in immediately, seeking shelter. Others try and follow the heat back to its source. They seem to have all but forgotten Castiel, now that his purpose to them has been served, and Castiel thinks it’s just as well. His part here is finished; he spreads his wings and rises from his perch back to the cold, sterile waters where the heat hasn’t quite reached, and leaves the rest to the echoes of his friends.

 

———

 

In the late twentieth century, a German scientist named Günter Wächtershäuser posited that life, in the broadest definition of the term, originated from a series of complex chemical reactions on the surface of hydrothermal vents, beginning with the synthesis of iron sulfide, and its interactions with other nearby compounds.

Such a lucky break, he marvelled, for iron and sulfur to exist in the perfect proportional quantities to allow this to happen.

Now it is happening again. And Wächtershäuser’s theory still holds true on all counts, except for one.

Castiel pauses in his upward glide, eyes sweeping over the spot where, ages ago, the Winchesters died. An unremarkable stretch of road, a handful of miles from the canyon rim, and yet he only has to squint his eyes just so to see it all again: Dean nodding off behind the wheel, Sam already fast asleep. Clouds half-obscuring the moon and fog swallowing up the headlights. And then the smoldering wreckage of the Impala, smashed full-speed into a towering tree just off the side of the too-narrow shoulder. Sam and Dean’s bodies mangled inside. Their blood staining Castiel’s hands even as he gathered their souls into himself and bore them personally into Heaven.

The blood is still here, soaked deep into the land. Traces of sulfur in the iron, and the two elements interacting with one another. Catalyzing. It’s the demon blood, Castiel realizes. Sam’s demon blood, vestigial, nigh-undetectable. Yet still here.

Nobody, not even Sam, had given it much thought in ages — first due to that trademark Winchester stubbornness to _play through the pain_ , and then it just — faded into irrelevance. They had other priorities. People to save. Things to hunt. Besides, Sam has redeemed himself a thousand times over, if not more; he is no more demonic, and the composition of his blood no more damning, than Castiel is human.

Still, the demon inside Sam never truly went away. Subsided, yes; it had retreated so far back into Sam’s biology that even the most powerful of angels barely suspected its presence. But it was always there, those faintest traces of Hell, dormant inside him until the day he died.

And it’s here even now, eons later. And just as Sam had wrestled his darker nature into submission through sheer force of will, so too the last remnants of that demonic biology are now subsumed and transformed by Winchester blood. By the forces of their long-departed souls, etched deep into the planet.

Sam provides the conditions required for the emergence of life, and Dean allows for it to be sustained into the next stages of its evolution. Even here, they complement one another — though, true to their natures and their relationship, many of the areas where heat and sediment and sulfur and iron come together will pressurize, boil over, and explode.

Those areas, too, will create new life someday.

Lucky break, indeed.

 

———

 

He wonders if he should tell Sam about the life he’s observed on this new Earth, and the role he and Dean play in its emergence.

One day, he thinks. One day, he will find the time and the words to explain to Sam — to both of them — the full ramifications of their existence, in whatever traces that their departed souls have left behind. But that, too, is a heavy responsibility, and Castiel has never liked seeing the weight of the world pressing down on Sam’s shoulders. Just as it will take billions of years for his home planet to grow into a state that he would recognize, so too will it take several more eons to fully heal the scars that the old Earth has left upon Sam’s soul.

One day. They'll get there one day.

Castiel slips between dimensions with a flutter of his wings and reenters the bunker in his human form. Sam’s door is ajar now, and he feels an echo of that deep-sea warmth spreading through him as he knocks.

“Come in,” Sam calls, and then, “Hey, Cas.” He’s stretched out on his half of the bed, thumbing absently through an LSAT study guide, and when he meets Castiel’s eyes his face softens into the warmest of smiles.

Castiel closes the door behind him.


End file.
